The objective of the proposed investigation is to define the relationship between normal and malignant tumor vasculature in the rabbit to obtain information of potential use to clinical cancer diagnosis and therapy in two distinct areas. The two basic areas are: (1) a study of the general characteristics of neovascularity so that pharmacologic manipulation of tumor perfusion can be used to increase perfusion and thus more selectively deliver tumoricidal agents (i.e., beta-emitting microspheres or chemotherapeutic agents) and diagnostic intravascular contrast agents, (2) a determination of the differences in attenuation coefficient between malignant and normal host tissue using computer tomography (CT) scanning. Attempts to improve the diagnostic precision of CT scanning could then be systematically studied using intravascular contrast agents, and these agents could possibly be more selectively delivered to the tumor using the data obtained in the preceding objective. Host organ and tumor perfusion would be studied in high (kidney), intermediate (liver, spleen, testicle), and low (muscle) perfusion organs. Using microspheres with different radioactive tags, resting, post-vasoconstrictor (norepinephrine) and post-vasodilator (prostaglandin E1, acetylcholine) perfusion can be determined for each tumor-host organ combination. Then, after selective arterial catheterization of the tumor bearing organ and the appropriate pharmacologic intervention, beta-emitting microspheres would be administered and animals studied by radioautography and survival against controls for therapeutic effect. For the CT studies ((2) above), host tissue and malignant attenuation coefficients would be established using a 3 second body scanner. A systematic study of intravenous and intra-arterial iodinated contrast agent (Renografin) with and without intravascular pharmacologic intervention would establish a standard against which to compare more tissue-specific contrast agents (radiopaque vesicles, perfluorocarbon compounds) for their diagnostic usefulness.